1. Field of the Invention
The present invention relates to a socket for an electrical part accommodating an electrical part such as semiconductor device (which may be called hereinlater “IC package”).
2. Related Art
A conventional example of such a socket for an electrical part is, for example, disclosed in Japanese Patent Application Laid-open Publication No. HEI 8-88063 as an IC socket. This IC socket has a socket body to which a number of contact pins are arranged, and contact portions of these contact pins contact side surfaces of solder balls as spherical terminals of an IC package.
The contact pins are formed from a sheet of plate by punching and then bending the plate so that the contact pin has, at its upper end portion, a contacting surface having wide area so as to abut against the side surface of the solder ball when assembled.
The contact pins of the structure mentioned above are divided into two or three groups, in which the contact pins in the respective groups are formed with elastic contact pieces, by which opposing forces are caused to thereby prevent the terminals from being offset in every direction including lateral and transverse directions and hence to suitably ensure mutual contacting positions of the contact pins between the respective terminals.
However, in such conventional structure of the contact pins, since the contact pins are formed by punching out the plate and then bending the punched out plate member, these workings involve many working steps, and in addition, in the bending working, it is obliged to select a material for the plate member that can endure the bending working, which limits the materials to be selected. For example, as such material, beryllium copper is generally utilized, but this material has a fear of being deteriorated in elasticity because of influence of heat.
Moreover, since the contact pin is displaceable in a direction perpendicular to the contact surface having a predetermined width, it is necessary to ensure a large movable area in the socket. In addition, the contact surface of the contact pin is contacted in a surface-to-surface fashion to the spherical terminal to thereby establish electrical connection, and then, there is a fear of making worse the electrical conductivity in a case where the surface of the spherical terminal is coarse.